In Linlibertine.svg, there are two groups of chars: i.e.
<hkern g1="f,longs,uni1E1F,f_f" g2="parenright,bracketright,braceright" k="-37" />
This line means: If there is an f followed by parentright, reduce the horizontal advance by -37 (add 37).
Therefore to quickly check if two characters need kerning assign an index to the second group (g2 or u2)
and assign to every unicode in the first group (g1 or u1) this index, then sort these tuples after their
name (for binary search). Because the same unicode char can appear in several g1s, reduce this multiset,
ie all the ("name1",0) ("name1",1) to ("name1",[0,1]).
Now the g2s are converted in the same way as the g1s.
Whenever two consecutive chars are being printed try to find an
intersection of the list assigned to the first char and second char